A rotary cone rock bit is adapted to be connected as the lowest member of a rotary drill string. As the drill string is rotated, the bit disintegrates the earth formations to form an earth borehole. The bit includes individual arms that extend angularly downward from the main body of the bit. The lower end of each arm is shaped to form a spindle or bearing pin. A cone cutter is mounted upon each bearing pin and adapted to rotate thereon. Individual bearing systems promote rotation of the cone cutters. The bearing systems have traditionally been roller bearings, ball bearings, friction bearings and/or a combination of the aforementioned bearings. The cone cutters include cutting structures on their outer surfaces that serve to disintegrate the formations as the bit is rotated.
The rotary rock bit must operate under very severe conditions, and the size and geometry of the bit is restricted by the operating characteristics. Some means for locking the cone cutter on the bearing pin must be provided. Traditionally, the locking function has been performed by a ball bearing system although other systems are known. The ball bearing system is used almost exclusively to retain the cone on the bearing journal and generally does not carry radial loads. Thus, a substantial portion of the available bearing space is wasted as far as radial capacity is concerned. This is especially critical in a small bit where bearing space is already minimal. The present invention allows a larger percentage of bearing space to be utilized for carrying radial loads thus increasing the bearing capacity of the bit.